Improvement in stone-drills



PATENT OEEICE.

WILLIAM D. MCOLURE, OF CONSTITUTION, OHIO.

IMPROVEM ENT IN STONE-DRILLS.

Specification forming part of Letters Patent No. l0I,290, dated March 29, 1870.

To all whom it may concern:

Be it known that I,W.D.MOGLURE, ot'Gonstitution, in the county of Washington and State of Ohio, have invented a new and useful Improvement in Drills; and I do hereby declare that the following is a full and exact description of the same, reference being had to the accompanying drawing, and to the letters of reference marked thereon.

This invention consists of a drill of peculiar construction which is intended for use in boring out the eyes of grindstones.

To enable others skilled in the art to make and use my invention, I will now proceed to describe fully its construction and operation.

In the drawing, A represents the shank or body of the drill, which may be constructed iu any proper manner. b represents the point, and b' b the wings or'cuttingedges.

It wll'be observed that the win gs form with the center line of the drill an angle of about forty-five degrees. They are twisted, ofcourse, in reverse directions, and taper gradually from their cutting-edges to the shank. The point which is formed by the union of the Wings with each other and the shank consists of a slightly-curving line which is placed at right angles to the transverse l-ine ofthe drill. The

Apeculiar t'orm produced by this construction is especially adapted for the use for which it is intended. The point, being blunt, cannot be broken; nor is it readily worn away by the stone. The wings are placed at such angle that they chip out the stone, instead of grinding it out. In practice it has been found that it will bore much more rapidly and wear much longer than any .other known form.

Having thus fully described my invention, what I claim as new, and desire to secure by Letters Patent, is-

A drill having its wings b and point b arranged as described, for the purpose set forth.

This specification signed and witnessed this 12th day of November, 1869.

WM. D. MCCLURE.

Witnesses A. W. MoCoEMroK, WM. S. BowMAN. 

